Soil structure is an important physical property of soil that relates to the arrangement of the solid parts of the soil and of the pore space located between them. As such, soil structure is important for soil function, plant growth and animal production. The benefits of good soil structure for the growth of plants include: reduced erosion due to greater soil aggregate strength and decreased overland flow; improved root penetration and access to soil moisture and nutrients; improved emergence of seedlings due to reduced crusting of the surface and; greater water infiltration, retention and availability due to improved soil porosity.
Cultivation generally leads to a decline in soil structure as mechanical manipulation of the soil compacts and shears soil aggregates and fills pore spaces. Continued cultivation and traffic also leads to compacted, impermeable layers or hard-pans within a soil profile. Irrigation also leads to a progressive decline in soil structure over time as aggregates break down and clay material is dispersed as a result of rapid soil wetting.
A number of approaches have been taken to preserve and improve soil structure, including increasing organic content by incorporating pasture phases into cropping rotations; reducing or eliminating tillage and cultivation in cropping and pasture activities; avoiding soil disturbance during periods of excessive dry or wet, ensuring sufficient ground cover to protect the soil from raindrop impact, and applying gypsum or calcium carbonate (lime) to exchange sodium ions with calcium ions, and thus to improve soil condition, permeability and infiltration. However, application or addition of gypsum or calcium carbonate may not be efficient enough for precision agriculture and conservation tillage systems due to their insolubility, high relative cost, and slow rate of effect.
There is a need for compositions or methods for improving soil structure that overcome one or more of the problems associated with known compositions or methods or which provide a useful alternative to known compositions and methods.